There is a continuing need to decrease the size of multilayer ceramic capacitors (MLC's) in order to use less space on circuit boards and to reduce costs. A decrease in size and cost can be achieved by developing ceramic materials with higher dielectric constant (K) and by manufacturing MLC's with thinner dielectric layers, typically 25 microns or less. While ceramic dielectrics with K of 15,000 or more are known, these are usually based on high lead materials such as lead magnesium niobate, or lead iron niobate and the like. Apart from the potential health hazard of processing powders with a high lead content, these materials also tend to have certain undesirable properties for MLC applications, such as relatively low mechanical strength, low chemical durability, and low K at MHz frequencies.
High dielectric constant materials based on barium titanate are also known (e.g. Burn, Raad and Sasaki, Proceedings of the Capacitor and Resistor Technology Symposium (CARTS), Amsterdam 1989). However, grain size is typically more than 5 microns, so that across each dielectric layer there exists a number of grains insufficient to achieve high reliability if the layer thickness is less than 25 microns. High dielectric constants with small grain sizes have been reported for solid solutions of barium titanate and barium zirconate made by wet chemical processing such as hydrothermal (Neirman, J. Mats. Sc. Vol. 23, p. 3980, 1988) or alkoxide (Mc Sweeney, Proc. First Int. Conf. on Ceramic Powder Processing Science, Orlando Fl., 1987). These solid solution compositions are not suitable for MLC's with thin layers because the Curie peak (or Curie Temperature) is above 25.degree. C. and the variation in dielectric constant with temperature is too large. Compositions with a Curie Temperature above 25.degree. C. have a dissipation factor unsuitably high for MLC's with thin layers. Thus, there is still a need for a barium titanate-based ceramic dielectric material that has a high dielectric constant, a fine grain size and a Curie Temperature below 25.degree. C.